The majority of electrical devices and equipment in use, domestically, and in industry and commerce are supplied by power derived from an alternating current supply which operates at a nominal frequency of 50 or 60 Hz. Power supplies operating at such low frequencies enables power to be transmitted very long distances without unacceptable losses resulting from the impedance of the power supply network such as would occur if a higher frequency was used.
One way of joining conductors carrying such low frequency power supplies is to use an inductive coupler. Essentially, such couplers comprise a transformer which can be physically split into two separate parts, a primary or input section and a secondary or output section. When the two parts are together magnetic coupling takes place between the primary and the secondary sections to transfer electrical power between them. Many types of material have been used to enhance the magnetic coupling between the primary and secondary sections and these range from conventional soft iron through Swedish iron to sintered ferrite cores having a variety of forms. Irrespective of the material used for the core when the inductive coupler is handling a low frequency such as 50 or 60 Hz a large quantity of material is required for the core to provide an efficient power transfer between the two sections of the inductive coupler. By using more exotic and thus more expensive materials for the core some reduction in size can be achieved over that required for, for example, a soft iron core. However, even the most sophisticated inductive couplers used for mains power are still of a substantial size.
In many situations the substantial size of such inductive couplers is a problem. This is particularly true in the aerospace industry in submersible craft and in the sub-sea oil and mining industries where space is at a premium. In general, any reduction in the size of the magnetic core results in a reduction in the coupling efficiency and this is also unacceptable.